Deciding between an automatic or manual transmission can significantly impact your driving experience and budget.

In our tests, we've found that in some cars a manual transmission can improve gas mileage by a significant 2 to 5 mpg, compared with an automatic, and can cut a car's price by $800 to $1,200.

At higher speeds, you can switch gears to a higher level. By doing so, the transmission allows you to benefit from more of your car's power, rotating the wheels more quickly. Modern transmissions come ...